Combustion chamber and draft system therefor



June 14, 1932. R. D. DE WOLF COMBUSTION CHAMBER AND DRAFT SYSTEMTHEREFOR Original Filed May 1, 1926 6 Sheets-Sheet l -SEPA/FATORINVENTOR ATTORNE III lIII llllrrllll'll ll! I'IIIL June 14, 1932. D fDEWOLF 1,863,397

COMBUSTION CHAMBER AND DRAFT SYSTEM THEREFOR Original Filed May 1, 19266 Sheets-Sheet 2 NVENTOB I V %zs A EY June 14, 1932. 5 WOLF 1,863,397

COMBUSTION CHAMBER AND DRAFT SYSTEM THEREFOR Original Filed May 1, 19266 Sheets-Sheet 5 June 14, 1932. R. D. DE WOLF 1,863,397

COMBUSTION CHAMBER AND DRAFT SYSTEM THEREFOR Original Filed May 1, 926 6sheets-Sheet 4 @Ai%3:"2f f ZSATTOR s June 14, 1932. R. D. DE WOLFCOMBUSTION CHAMBER AND DRAFT SYSTEM THEREFOR OriginaIF'ile ay 1. 1926 6Sheets-Sheet 5 INVENTOR 3323 7%Z9ATTOR EY June 14, 1932. DE WOLF1,863,397

d Ma 1, 1926 I 6 Sheets Sheet 6 l 5 Z Z5 in i and @ifiQient-comhnstionof the fuel may be 1 inggthe, air; ivhich is forced ordrawn :into the'pointedout in theclainis at the endv ofthe a lustratinq oneembodi-nientof theinvention.

oneavall ofthe combustion chamber, taken.

Patented June 14, 1932 .etsmmes m oe me rcomausnon CHAMBER ANnnRAF'rSYSTEM THEREFOR or-igi nal applioation flled liay 1,--1926,- -Ser1a1 No.106 123. -;Div ided -and-th-is aPmicationfiled/April :19,

1928.--Seria1' 'bns'tion chambers, so lhatqlnore; satisfactory bt'ained;at;v alldtimes va ary'ingiileads A; further object of theinvention isthe -provision ofinapro-ved; meansl for; preheateven A 1 under wvidely:;It isan additionaL-objeet ofthe invention to provide, a combustion.ehaniber having an improved shape which allows room for ex--2aupansiono the'fiflmetand of the; products of Y combustion at the;points .Where the; need for such expansion is greatest, and Which-isso Idesigned that {the tendency of. fusecl -ash or re egate; adhere-$ithesual s O ::'l h '=QQm tion a hamberfis reduced to a inininiuni.

Still; another-object is theprov-ision of a rsystem of eombustion and ofm-clombustion chamber which are especially; adapted-for the -,efiieientand-satisfactorv combustion of fuel -3 in n pu-lverized.orfinelyydi-videdstate.

:To these and other ends the invention re- IISid6SiI1Teert'ain;irnprove1nents and combina- ;..be} understood that many-of thefeatures are I applicable equally Well to ,othe naces=or-hurning otherkinds :tions of ipart-s, all as-ywillbaherei-nafter; more llfiilly rideseribed,i;;tl1e,a novel vsfeatures :=,.hen1g specification.

-ln the drawings:

Fig. I is a side elevation-bfafurnace'ilf F 'igsQ isafrontelevationthereon-With parts broken"au ay-inorder to show, the

structure; better.

is averticalsectlonal View through approximately "on the line 3-3 of-Rig. 2.

ff 4 a similar verticali-seetional view,

an F ig.= 5};is, a :vertiealrsee ional; view taken 1 combustion chan1ber, with parts ish ssmately on the 1 line 7--7 of.-

,part oofone of the walls: of; the chamber,- gillustrating certain 1$*ua ils of, con- =struetion and especially adapted for burningPate-ntNo. 1,810,203, ion in like. 7

orally by :iak nrapproximately on the lines of a,

f; the upper; ipart {oi the oavn; in

seot-ignr the isec tion being taken appro n nately. on the line 6 -6lofgEigr 8.

Fig; '1'; is a verticalseetionalview through part oft-the; upper,pontoniofith cmllbu io chamber, the section being;taken apprgxt 8 is21-;VQItlCtl sectional view through part. of the upper portion ,of thegGQIXlbLlSfiiQD Ql111l1b8I,-, 5th n atelynon the line 8+8'of Fig.5 andat right; angles to the plan e section being t-aleen approgcii a ij-Fig; 9-is an elevation of part offthe front Wall of the furnace, withthe outer; covering removed and w th parts broken:

aw y- 0t th sam 9. etionalview t ee bus i -'F ig, 10 is a horizontalsection port on of 'Wall' ;sho vn in Fig;

:1 F 1g. 1131s a vert-1c ,perspective vie-Wei; a part-of l of thecombustion chamber,

Fig. 12 is'a the; front-val i lust tingcerta eta l The same referencecharaotersarefierito the ;san1e parts throughoutthe several-views.

The furnace shown in this appli eationgis rfuel in pnL butii shoulverized or finely: divided form,

yp s far of fu This applicationis a division of-my -application Serial?N 0.,- 106,123,; filed May;;1,- 1926, IIIZlCQSpflHdgllhG In theembodiment illustrated in' draw-e90 -;ings, there is shown a furnacehaving a gcom- .bust-ion chamber numeral 21 this combustion clmmbeiibeing -substantia1l -1et atthe upper portion of its ream-side.

;indieated generally :by the yreetangulan-and having an outpass out ofthe combustion chamber. able water tubes or other boiler elements,indicated diagrammatically by dotted lines in Fig. 1, are placed withinthe boiler enclosing casing 22 so that they absorb the heat resultingfrom combustion. A suitable duct 23 is connected to the structure 22toremove the products of combustion therefrom, and this duct preferablyis connected to a stack or other appliance for creating a draft in thefurnace.

The walls of the combustion chamber and of the boiler enclosingstructure may be, constructed in any suitable manner. In the embodimenthere shown, the combustion chamber is of considerable height, and theform of wall construction used is especially adapted to combustionchambers of such form.

The wall construction is shown in detail in the parent a division, anditwill, therefore, be described only briefly in this application,reference be ing had to the parent case for more complete description ofthe details.

In a furnace structure of considerable height, the weight ofthe upperportion of the structure often bears excessively on the lower partthereof. Furthermore, if the lowerportions of the walls have to berenewed for any reason, it is usually necessary to tear down the wholewall, as there is nothing to support the upper portion of the wall whenthe lower part is removed. To eliminate these undesirable features,there has been provided in the present instance a skeleton or frameworkupon which the walls are supported at intervals. This skeleton not onlybears the weight of the upper part of the walls, so as to reduce theweight on'the lower. portion, but also acts as supporting means for theupper portion even when the lower part is entirely removed for repairsor replacement. v

This framework or skeleton comprises up- "rightbeams 25 spaced atintervals along the outline of the walls of the furnace, and pro videdwith suitable braces and anchoring meansx Angle bars 26, best shown inFig.

i 12, are fixedhorizontally to the upright beams 25 so that they providea series of vertically spaced flanges extending inwardly from the beams25 toward the center of the furnace. The horizontal flanges formed bythese angle bars 26 constitute supporting ledges on which the walls'ofthe furnace aresupported at vertical intervals. Each section of wallsupported on one flange is independent' of the sections above andbelowit, so that it neither bears against the section below nor carriesthe Weight of the section above. On each of the flanges26 and oppositeeach of the beams 25 there is mounted a hanger block 27 which is clampedsecurely to the adjacent beam25 by clamping members 28 best shown inFigs. 10 and 11. These hanger blocks 27 Suitcase of which thisapplication is 1 are formed with cut-out portions 29 and wing portions30, as illustrated clearly in Fig. 12. i On top of each hanger block 27there is built up a column of similar hanger blocks 31, these latterblockshaving similar cut-out portions 29 and wings 30, but beingslightly shorter, than the blocks 27 so that the lowerinostblock 27which rests on the shelf 26 projects slightly "further inward than thecolumn blocks 31 which are superimposed on it. This is shown clearly inFigs. 10, 11 and 12. Each ofthe blocks 31 in thepolumn is secured; tothe adjacent beam 25 by clamps 28, and the column of hanger blocksextends upwardly from one flange 2G to a point just' the cut-out portion29 behind the wing of the hanger block. Thus each'brick is kept in placeand prevented from falling out of the wall. Each brick also has aportion extending across the face of the hanger block to approximatelythe center line thereof, as shown in Figs. 10 and 12 so that it meets asimilar extension on the corresponding brick on the otherside of thesame'hanger block and thus completely protects the hanger bloik fromheat by covering the entire face thereof.

The lining bricks 35 which cooperate with the long hanger blocks 27 aremade narrower than the other bricks which cooperate with the shorterblocks 31, so that the inner surface of the finished wall 1S smooth, asshown in Fig. 11. The brick next above'each of the long hanger blocks'27 rests upon the'ledge formed by'the inwardly projecting end ofthehanger block, and thus the lining bricks are divided intoindependently supported vertical columns resting upon the long hang erblocks 27 which, in turn, are supported by the ledges 26. The narrowlining bricks which are placed opposite the long hanger blocks rest uponand form part of the column of bricks immediately belowthose'long-hanger blocks, as shown clearly in Fig..11. In order to allowfor expansion'. cracks'37 are left between eachcolumn of hanger blocksand lining bricks and the next column above t. These cracks arepreferably filled-with some heat resisting compressible packing, forexample flaked asbestos.

It will now be seen that the walls are divided into independentlysupported vertical units carried by the anglebars 26 attached to theupright beams 25. If repairs tof the wall are needed at any point, alimited sec- Leeann? tion of the wall may be torn down withoutaffecting-the sections above it. Thus an efficient form of constructionis provided, in which the cost of repairs and the time con sumed thereby.are reduced greatly. Also, a wall construction in this form may becar'- ried to any desired height, since the weight is supported by thebeams and does not cause undue crushing strain in the lower parts of'thewall.

Prefera bly the side walls of the combustion chamber, at least in thelower portionthereof, are flared outwardly so that the combustionchamber has a downwardly increasing cross section, as shown in Figs. 2and 5. .Vhen the walls are formed in this manner, there is less tendencyfor clinker to adhere to the walls, since the liquid drops of fused ashor other products of combustion will have a tendency to drop off of thewalls into the ash pan 40 rather than to run down the sides of the wallsand solidify thereon. This flared formation of the walls of the combustion chamber is also useful for another purpose. As will be explained ingreater detail below, the fuel is preferablyadmitted to the top of thecombustion chamber, and the flame travels downwardly to a point near thebottom of the chamber, then turns and ascends again. The greatest crosssectional area is needed at or near the point where the flame turns, andit is just at this point that the increased area is provided in thepresent construction. Also. by increasing the cross section of thecombustion chamber in the downward direction of flame travel, additionalspace is provided where it is most needed for the expansion of theproducts of combustion. i

The top wall of the combustion chamber maybe formed in any suitablemanner. For

instance, as shown in Figs. 3, 4 and 5, beams mav extend across the topof the combustion chamber and hanger blocks 46 may be secured thereto,by clamps 47, fire bricks 48 being supported from and held in place bythe hanger blocks 46.

As has been mentioned before. this combustion chamber is especiallyadapted for burning pulverized or finely divided fuel, a though it maybe used with fuelof other kinds or forms. There is shown in the presentinstance a pulverizer 50 adapted to receive coal by gravity through achute .51. A separator 52 may be provided at the outlet of thepulverizer for separating the coarser particles from the finer ones andfor returning the former to the pulverizer. blower 53 draws thepulverized fuel up from the pulverizer 50 through the separator 52 anddelirers it through a conduit 54 to the fuel inlet 55. As shown in Fig.6, a plurality of fuelinlets may be formed in the combustion chamber,and a separate pulverizerandblower may he -used for each fuel inlet ifdesired, or a single pulverizer and blower maybe used for two or more ofthe inlets. The fuel inlets in the present instance are shown asextending through the top of the combustion chamber, but other suitablepositions might be used if deemed preferable. I

The fuel, after entering the combustion chamber through one or more ofthe inlets 55, will pass downwardly through the combustion chamber,burning as it travels. At a point near the bottom of the chambentheflame will turn and pass upwardly again and into the boiler enclosingstructure 22 and thence to the stack. If desired, suitable air or waterpreheaters may be provided in the connections to the stack or elsewhere,and suitable forced draft mechanism may be employed. e i

'In order to promote complete and efficient combustion of the fuel, itis desirable to ad m'it air into the combustion chamber in ad dition tosuch air as may be admitted along with the fuel, and it is alsodesirable to be able to control the air varying conditions. The meansfor doing these things will now be described.

Covering members 60, best shown in Figs; 10, 11 and 12, may be fixed tothe outer edges of the upright wall beams '25. Thus, the walls of thecombustion chamber are, in effect, made hollow, and are provided with aseries of substantially vertically extending conduits or ducts. Thecovering member forms one of the sides of each of these ducts,

the lining members 35 formanot-her side, while the beams 25 31 serve aspartitions to separate eachcondulit from the adjacent conduits at eitherSIC e.

The conduits in'the front wall of the com bustion chamber may be dividedinto upper and lower portions by baflle walls 161, as

supply to adapt it to and hanger blocks 27 and shown in Figs. 3 and 4,,while the conduits in the sidewalls may extend throughout the fullheight of the combustion chamber. It should be understood that the termsfront andv side are used simplyfor ease of .description, and are not ingsense. The upper conduits inthe front wall, above the baffle walls 61,,may be designated by the numeral 62, while the lower conduits in thefront wall are marked 63.. The conduits in the side walls are denoted64.

Openings wall of the combustion chamber leading from each of theconduits 62 into the chain ber, each of the conduits having a series ofthese openings vertically spaced from one as shown especially in Figs.3, 4

another, and 5. In order to prevent direct radiation of'heat through theopenings 65, baflie plates 72 may to be taken in a ,limit- 65 may beformed in the front beplaced opposite each of the openings, with 1n thechannels 62 and'slightly spaced'from' if outer surfaces of the liningbricks 35, as shown in Figs; 3, 4 and 12. -These battle members 72 may.rest against flanges 73 formed on the hanger blocks 27 and 31, and maybe held in place against these flanges by vertical bars74 (Fig.9) whichextend over several of the bafiie plates 7 2 and hold them inplace,these bars 74: being held inwardly against the baflie plates by crossbars-75 which have their ends set against the "clamping devices 28, asshown in Figs. 9 and 10. Posts 76 hold the baflle plates 72 verticallyspaced from each'other, so that each plate will be properly placed inalinement with one of the openings 65, as shown in Figs. 3, 4 and 9.These baflie plates 72 therefore prevent heat from radiating directlyout through the openings against the cover member 60 to such an extentas to injure this covering, butthey do not interfere with the passage ofair from the conduits 62through the openings 65, for the air may flowaround the edges of these baffle plates as indicated by the arrows inFigs. 3 and 4, j r

A part of the conduits-64 in the side walls of the combustion chamberare connectedat their upper ends through openings 66a to aconduit 66which extends around the sides and the front of the combustion chamber,and is connected through an opening 666 to the upper ends of theconduits 62 in the front wall. The openings 666 from the conduit 66 intothe conduits 62 is preferably controlled by a plurality ofdampers 67(Figs. 3 and 4E) having operatingmembers 68 so that the dampers may beopened or closed, as desired, either individually or in gangs. Theconduits 64 in the side walls have inlet openings 69 at their lowerends, these openings being controlled by dampers 70 which may beprovided with suitable operating means.

If the dampers 67 and 70 be opened, it will be seen that air may enterthe conduits 6% at their lower ends and pass upwardly therein, in thedirection of the arrows in Fig. 5. As the air passes upwardly throughthese conduits, it becomes heated by contact with the hot lining wallsof the combustion chamber and serves at the same time to absorb heatfrom the walls and to cool them considerably. Thus the effective life ofthe furnace lining is lengthened, because the bricks, when keptcool bymeans such as this. do not burn out as rapidly as when no coolingmeansis. pro.-

: vided.

' The heated air rising through the conduits 64 passes through theopenings 66a is collected by the conduit 66 and carried around the sidesof the combustion chamber to the front, as shown especially in Figs. 6and 7, where it passes through the openings 66?) into the up perends ofthe conduits 62. The air then flows down these conduits andthrough theopenings 65 into the combustion chamber in proximity to the burning fueltherein. This provides some of the additional air necessary to obtainproper combustion of the fuel.

When the furnace is being operated at a low rate, some of the dampers 67and 7 0 may be fully or partially closed, so that the supply of airflowing into the upper ends of the conduits 62 is limited. It should benoted that the air in these conduits flows in substantially the samedirection as the travel'of the flame within the combustion chamber, andcomes first to those openings 65 which are nearer to the fuel inlet. Inorder to reach the lower openings 65 which are farther from the fuelinlet, the air must flow through av greater length of the conduits 62,which will, of course, produce greater frictional resistance to theflow. Thus the air tends to flow into the combustion chamber through theupper openings 65, since this is the path of least resistance, ratherthan to continue along the conduits and enter the combustion chamberthrough openings nearer to the bottom thereof. In this way, practicallyall of the air flowing in the conduits 62 when the furnace is operatingat a low rate will enter the combustion chamber through openings 65comparatively near the fuel inlet, where it is most needed for efiicientcombustion, and very little air will find its way through the-loweropenings 65. i

When the furnace is being operated at a high rate, however, a greaterquantity of air is admitted to the conduits 62, and an in creased amountof fuel is introduced into the combustion chamber. ,Under theseconditions, it would be undesirable to have the air distributed in the.same proportions mentioned above, for if most of the air in the conduits62 passed through the upper openings 65, it would have; too great acooling 7 effect upon the burning fuel. At high load,

therefore, a greater proportion of the air should pass by the upperopenings 65 and should continue along theconduits 62 so as to enter thecombustion chamber'through some of the openings 65 farther down. i

This desirable result is accomplished largely automatically by thepresent construction. hen large quantities of air are flowing throughthe conduits 62, it is obvious that the greater part of the air is nolonger able to pass through the openings 65 near the upper ends of theconduits, for the resistance to the flow of such a large amount of airthrough these openings is too'great. Consequently a large part of theair flows on down the conduits 62 and passes through other openings 65farther away from the-fuel inlet. Furthermore, when the furnace is beingoperated at a higher rate, the so-called chimney effect 7 is morepronounced, and will produce a greater draft in the lower part'of thecombustion chamber than in the upper part thereof. This will tend todraw a greater quantityof air through the openings 65 in the lowerchamber.

portions of the conduits 62 than through the openings in the upperportions. In this way the air is distributed differently-when thefurnace is operating at difierent rates or under different loads. Thedistribution, as above p inted out, is'largely automatic, and thepresent construction is very effective promoting efficient combustion atall times in furnaces which must be operated at different rates fromtime to time.

The conduits 63 in the lower portion of the front wall of the combustionchamber may be provided with inlet openings at their lower ends, theseopenings. having dampers 81 controlled by operating members 82. A partof these conduits (for example, each alternate conduit) may havevertically spaced openings 83 extending through the wall of the furnaceinto the combustion chamber, as shown in Fig. 4, these openings 83having battle plates 72 similar to those associated with the openings65.

These conduits 63 which open into the combustion chamber at 83 thus formadditional means for admitting air into the combustion chamber inproximity to the path of flame travel. The air entering the conduits 63through the inlets 80 and rising through the conduits becomes preheatedby contact with the lining walls of the combustion chamber and serves tokeep these walls cool, as is the case also with the air in conduits 62and 64. Thus the conduits 63 having the openings 83 form a means foradmitting preheated air to the lower part of the combustion chamber inproximity to the path of flame travel, and

also a means for cooling the walls of this part of the combustionchamber. When the furnace is operating at a low rate, the dampers 80 maybe placed so that little or no air enters the lower part of thecombustion chamher through the openings 83. When the rate is increased,the greater volume of air required may be admitted partly by allowingair to enter the openings 83 and partly by allowing an increasedquantity of air to enter the combustion chamber by way of the conduits62 and openings 65.

The remaining conduits 63 which do not have openings 83 former. therein,are provided at their upper ends with openings 84 leading into a duct orconduit 85 which extends across the front of the combustion chamber, asshown in Figs. 1 to 4. These conduits 63 which open into the duct 85 areprovided with inlets 80 and dampers 81, similar to those provided forthe conduits having the openings 83 leading into the combustion- Theduct 85 is connected by a conduit 86 to the pulverizer 50, as shown inF 1. Thus the air passing through part of the conduits 63, and becomingpreheated therein, is collected in the duct 85 and conducted to thepulverizer, where it is mixed conduits tion chamber were connected bymeans of the with the 'fueliprior to the injection thereof into thecombustion chamber.

It was mentioned aboveithat part of the 64 in the side walls of thecombusconduit 66 to the upper ends of'the conduits 62 in the front wallof the furnace, The remaining conduits 64 in the side Walls Which arenot'so connected to the conduits 62 may open into a duct 90, best shownin Figs. 6 and '1', this duct 90having branches 91' leading to air inletopenings 92 adjacent and preferably surrounding the fuel inlet openings55. Those conduit-s 64 which are thus connected to the inlets 92 haveair inlet openings 69 and dampers 70 to the inlets and dampers providedfor the rest of the conduits 64.

The inlet openings 92 provide means for injecting air closely adjacentto the fuel inlet, this being point at which air is needed and in whichit will be of considerable benefit in promoting efiicient combustion.

It willnow be seen that an improved combustion chamber has'beenprovided,- which is equippedwith means for cooling the walls thereof,this. cooling means serving also as air preheating means. Part of thevair' thus-preheated is mixed with the fuel" before its in j ection intothe combustion chamber; another partis injected-into the combustionchamber adjacent the fuel inlet; and other parts of the preheated airare arranged to enter the combustion chamber through openingsspaced inthe direction of fuel and flame'tra-vel and inproximity to the line oftravel thereof. A portion of this last mentioned quantity of an isconducted through passageways so. arranged that it chamber at pointscomparatively close-to the fuel inlet, and encountersincreasing resistance as it passes these points to enter the combustion chamber fartheralong the path of travel of the flame. Various dampersare arranged forcontrolling the quantity of air admitted to each part of the".combustion chamber. Thus a highly satisfactory and efiicient draftsystem. is disclosed, which has many advantageous and desirablefeatures.

Although the term fuinace has been used throughout this specification,it should be understood that this combustion chamber has been describedin connection with a furnace only by wayof example, andis not limited inits applicationto boilers or furnaces of any particular type, but may beused whereever any, sort 0 combustion chamber isdesired. 1 i V 1 Whileone embodiment of theinventionhas been, disclosed, it is to beunderstoodtthat the inventive idea may be carried out in a number. ofways. This application is therefore-not. to be limited to the precisedetails shown, but'is intended to cover all variations andmodi-ficm attheir lower ends, similar into the combustion chamber.

tends to enter the combustion" tions thereof falling within the spiritof the invention or the'scope of the appended claims I claim as myinvention: V

1. In a furnace construction, the combination with a combustion chamber,of means for admitting fuel thereto, a plurality of separate conduitsextending substantially vertically in a wall of said combustion chamber,said wall having a plurality of spaced openings leading from the lowerportion of one conduit into said combustion chamber, and a plurality ofspaced openings leading from the upper portion of another conduit intosaid combustion chamber, means for admitting air to the upper end of theconduit having openings in its lower portion, and means for admittingair to the lowerend of the conduit having openings in its upper portion.

2. In a furnace construct-ion, the combination with a combustionchamber, of means for injecting pulverized fuel into the top of saidchamber, a plurality of substantially vertical conduits in the frontwall and side walls of said combustion chamber, said conduits havinginlet openings leading from the conduits in the front wall into saidcombustion chamber, means for admitting air to the lower ends of theconduits in the side walls, means forconnecting the upper ends of a partof the conduits in the side walls to the upper ends of the conduits inthe front wall, and means for collecting air from other conduits in theside walls and introducing it into the top of the combustion chamberadjacent the inlet for said pulverized fuel.

3. In a furnace construction, the combination with a combustion chamber,of means for injecting pulverized fuel into the top of said chamber, aplurality of substantially vertical conduits in the front wall andsidewalls of said combustion chamber, said conduits having inletopenings leading from part of the conduits in the front wall into saidcombustion chamber, means for admitting air tothe lower ends of theconduits in the side walls, means for connecting the upper ends of apartof'the conduits in the side walls to the upper ends of a part of theconduits in the front wall, means for admitting air to the lower ends'ofthe rest of the conduits in the front wall, means for collecting airfrom the upper ends of a part of said last named conduits, and means formixing said collected air with .the pulverized fuel prior to itsinjection into the combustion chamber.

4. In a furnace construction, the combination with a substantiallyvertically arranged combustion chamber, of a plurality of conduits inthe front and side walls of said combustion chamber, mechanism forpulverizing fuel, means for leading pulverized fuel from said mechanismand injecting it into said chamber, means for admitting air to the lowerends of said conduits in a side wall of the chamber, means forcollecting air from the upperends of certain of said conduits havingadmitting means intheir lower ends and for admitting such collected airinto said combustion chamber in proximity to the fuel inlet, means forcollecting air from the upper ends of certain other of said conduitshaving admitting means in their lower ends and for supplying suchcollected air to the upper ends of certain of the conduits in the frontwall, such front wall conduits having inlets leading into said chamber,means for admitting air to certain other conduits in the front wall, andmeans for collecting air from said last named conduits and for mixingsuch air with the pulverized fuel prior to its in jection into saidchamber.

' ROGER D. DE WOLF.

